TRENCH CONSTRUCTION

  • Information provided in this installation guide is intended as a quick reference only and does not supersede requirements specified on project plans.
  • The trench or ditch should be wide enough to place and compact backfill around then entire pipe.
  • Refer to Table for recommended minimum trench widths. The design engineer may modify the trench width based on site specific conditions. 
  • For parallel pipe installations, allow space between pipes for proper compaction. Refer to Figure for minimum pipe spacing. *Spacing will differ for retention/detention systems due to the intended use of this product.
  • UP TO 600MM I.D.: M=300MM
  • MORE THAN 600MM I.D.: M=1/2 I.D.
  • Trench or ditch bottoms containing bedrock, soft muck or refuse, or other material unable to provide long-term uniform pipe support are unacceptable.
  • All unsuitable foundation shall be excavated before pipe installation proceeds.
  • Where rock or unyielding or soft foundation is present, the design engineer shall be contacted to determine the extent of excavation required.
  • If native soil can migrate into backfill, use synthetic fabric (geotextile) to separate native soil from backfill.

 

 

 

 

 

 

Trench Boxes:

Trench boxes provide a safe work area to install pipe in deep trenches or in soils that have insufficient stability. Always follow OSHA requirements when using a trench box.

The length of the trench box should be suitable for the pipe length. Nominal length for dual wall HDPE pipe is 6m although shorter lengths can be supplied.

The most effective way to maintain a sound system is to provide a ‘subtrench’ within which to place the pipe and backfill. The subtrench shall not be greater than 24” above the bottom on the trench as shown in Figure. Backfill and compact according to the design specifications within the subtrench. The trench box can be pulled along the top edge of the subtrench without affecting the backfill in the pipe embedment zone.

 

 

In installations not involving a subtrench, dragging a trench box should only be done if it does not damage the pipe or disrupt the backfill; otherwise, the box should be lifted vertically into its new position, again taking great care not to disturb the pipe or backfill.